John the Baptist was the forerunner of Jesus Christ. He was born to the elderly Zechariah and his barren wife Elizabeth (similar to Abraham and Sarah). Elizabeth was a relative of Mary, the mother of Jesus, and both became pregnant a six months apart. (Lk 1:41-42). Both were visited by the angel, Gabriel.
John grew up in the wilderness and preached in the wilderness. His message was for people to repent because the Kingdom of heaven is at hand (Matt 3:2).
John baptized his followers in the Jordan River, to signify the drowning of their old life and their emergence from the water into a new life. John, as did Jesus later on, ran into conflict with the Pharisees and Sadducees for whom he had sharp words (Matt 3:7-12).
John baptized Jesus, and proclaimed Him the Lamb of God who takes away the sin of the world. Jesus Himself appraised John in Matt 11:7-15.
John was much more than a prophet, surpassing his predecessors in greatness, and comparable to Elijah. But John’s generation did not accept him, alleging instead that he was demon possessed (Matt 11:17-18).
John’s role as forerunner to Jesus was alluded to in a prophecy from Isa 40:3:
The voice of him that crieth in the wilderness, Prepare ye the way of the LORD, make straight in the desert a highway for our God.
There is another prophecy, in Mal 3:1, that also alludes to John the Baptist’s role in preparing the way for Jesus Christ.
Behold, I will send my messenger, and he shall prepare the way before me: and the Lord, whom ye seek shall suddenly come to his temple, even the messenger of the covenant, whom ye delight in: behold, he shall come, saith the LORD of hosts.
John was beheaded 29 A.D. by Herod Antipas who imprisoned him in revenge for John’s condemnation of his incestuous marriage to his brother’s wife (Lk 3:19-20).
Herodias’ daughter, danced for Herod, who rewarded her by offering her whatever she wished. On the advice of her mother, she requested the head of John the Baptist on a platter. Herod was grieved at being requested to execute him, but having given his oath before witnesses, he commanded that it be done (Matt 14:1-11, Mk 6:14-28).